I ran some autos that looked like that once. Are you letting your media get dried out enough in between feedings/waterings? Stay with the nutes and such discussed above but make sure you are not over/watering/feeding where your soil is constantly soaked. Once I figured out that was my problem, I changed my routine. Auto's are a funny lot. Mine didn't green back up but I did end up with a decent harvest. You are way too far out time wise to be giving up on this plant !!! And possibly, don't believe everything the seed companies print on the package. (If that is your case) Just because they claim it's a 90 day plant doesn't mean anything. I have had regular seeds I purchased that turned out to be autos and vice versa.